Embodiments of the present invention generally relate to wind farms and more particularly relate to a system and method for automatic generation control in wind farms.
Wind turbines are used to generate electrical power from wind energy. Multiple wind turbines may be coupled together to form a wind farm, and multiple wind farms may be coupled to a power grid. The wind farms are required to provide a committed output power to the power grid for scheduling generation and maintaining load-generation balance. However, due to constant fluctuations in wind speed and in load coupled to the power grid, a difference may occur between a power injected into the power grid and the committed output power. The difference leads to variations in a system frequency, which necessitates a use of reserve resources to overcome such variations. In order to overcome the variation, the wind farms provide additional power control capability to the power grid to maintain the frequency.
In one type of control methodology, the power grid is managed by an independent system operator which directs owners of the wind farms coupled to the power grid to provide the additional power control capability and maintain the frequency in the power grid. The wind farm owners maintain the frequency by employing a primary frequency response, also referred to as frequency droop, and a secondary frequency response. The wind farm owners receive additional payments from the independent system operator for the secondary frequency response based on a control band and accuracy in providing a committed power for the second frequency response.
One type of secondary frequency response technique includes automatic generation control. The automatic generation control (AGC) is a system for adjusting power output of multiple generators located at various locations in the system, in response to changes in the system frequency and multiple tie-line powers of the interconnected power system. The automatic generation control employs various approaches to provide additional power for adjusting the power output. One approach includes using a centralized wind farm battery for providing the additional power to the power grid. However, such an approach leads to additional costs and associated risks such as a single point of failure in providing additional power.
In another approach, a distributed storage wind farm may be deployed to automatically provide additional power control. In such approaches, some of the wind turbines in the wind farm include an integrated energy storage element that may be used to supplement wind generated power and provide the additional power. In the described approach, wind turbine controllers of each of the wind turbine independently control the respective integrated energy storage elements.
It would be desirable for wind farms to have further options for addressing frequency variations and controlling integrated energy storage elements.